The disclosure relates to a miniature spectrometer and to a method for ascertaining a spectrum of the radiation that is reflected, transmitted or emitted by an object.
The disclosure proceeds from a miniature spectrometer and a method for ascertaining a spectrum of the radiation that is reflected or emitted by an object.
“A static polarization imaging spectrometer based on a Savart polariscope” (Zhang et al., Optics Communications 203 (2002), 21-26) describes a polarization imaging spectrometer (PIS) based on a simple Savart polariscope. It produces a two-dimensional intensity distribution that contains in one spatial direction the interferogram and in the direction that is orthogonal thereto the image information. Both components are present at the same time and must be separated from one another. This two-dimensional distribution is recorded using a two-dimensional CCD (charge-coupled device) detector. The PIS comprises an infinity optical system, a polarization interferometer comprising a polarizer, a Savart polariscope and an analyzer, an imaging lens and a system for recording and processing signals. The infinity optical system produces from the rays arriving at each object point beam bundles that are parallel in themselves at different angles. The resolution of the PIS can be set via the size of the CCD detector and the thickness of the birefringent layers that form the Savart polariscope. The resolution increases as the size of the CCD detector and the thickness of the birefringent layers increase. The spectral resolution is additionally dependent on the useful angular range, the refractive index contrast between the two polarization directions and the focal length of the lens between Savart polariscope and detector.